Most (good quality) outdoor furniture companies have an anodized or powder coated finish. This will allow the furniture to stand up to the exposure to the salt air.
You may also want to look at Teak furniture, but please be sure that the furniture has stainless steel screws.
As most things in life, you get what you pay for so be careful when looking at patio furniture from “Big Box” stores. They are not always taking into consideration the location of the store and elements that this furniture can be exposed to.